Natural 15-methyl and ethyl-15-epi-pge1

ABSTRACT

1. AN OPTICALLY ACTIVE COMPOUND OF THE FORMULA:   1-(O=),2-(R1-OOC-(CH2)6-),3-(H3C-(CH2)4-C(-OH)(-R2)-CH=   CH-),4-(HO-)-CYCLOPENTANE   WHEREIN R1 IS HYDROGEN, ALKYL OF ONE TO 8 CARBON ATOMS, INCLUSIVE, OR A PHARMACOLOGICALLY ACCEPTABLE CATION, AND WHEREIN R2 IS METHYL OR ETHYL.

United States Patent O 3,849,487 NATURAL IS-METHYL AND ETHYL-lS-EPI-PGE,Gordon L. Bundy, Portage, Mich., assiguor to The Upjohn Company,Kalamazoo, Mich.

No Drawing. Continuation-impart of abandoned application Ser. No.37,307, May 14, 1970. This application July 24, 1972, Ser. No. 274,643

Int. Cl. C07c 61/36, 69/74 US. Cl. 260514 D 2 Claims ABSTRACT OF THEDISCLOSURE Prostaglandin E -type compounds with a methyl or an ethylsubstituent at the C-l5 position and with the C-15 hydroxy in Rconfiguration are disclosed. These are useful for the samepharmacological purposes as the unsubstituted prostaglandins.

CROSS REFERENCE TO RELATED APPLICATIONS This application is acontinuation-in-part of my copending application Ser. No. 37,307, filedMay 14, 1970 now abandoned.

DESCRIPTION OF THE INVENTION This invention relates to novelcompositions of matter, to novel methods for producing those, and tonovel chemical intermediates useful in those processes. In particular,this invention relates to novel derivatives of prostanoic acid which hasthe following structure and atom numbering:

Various derivatives of prostanoic acid are known in the art. These arecalled prostaglandins. See, for example, Bergstrom et al., Pharmacol.Rev. 20, 1 (1968), and references cited therein. For example,prostaglandin E (PGE has the following structure:

In formulas II to IV, broken line attachments to the cyclopentane ringindicate substituents in alpha configuration, i.e., below the plane ofthe cyclopentane ring. Heavy solid line attachments to the cyclopentanering indicate substituents in beta configuration, i.e., above the planeof the cyclopentane ring. The side-chain hydroxy at 0-15 in formulas IIto IV is in S configuration. See Nature, 212, 38 (1966) for discussionof the stereochemistry of the prostaglandins.

Molecules of the known prostaglandins each have several centers ofasymmetry, and can exist in racemic (optically inactive) form and ineither of the two enantiomeric (optically active) forms, i.e., thedextrorotatory and levorotatory forms. As drawn, formulas II to IV eachrepresent the particular optically active form of the prostaglandinwhich is obtained from certain mammalian tissues, for example, sheepvesicular glands, swine lung, or human seminal plasma, or by carbonyland/or double bond reduction of a prostaglandin so obtained. See, forexample, Bergstrom et al., cited above. The mirror image of each offormulas II to IV would represent the other enantiomer of thatprostaglandin. The racemic form of a prostaglandin would contain equalnumbers of both enantiomeric molecules, and one of formulas II to IV andthe mirror image of that formula would both be needed to representcorrectly the corresponding racemic prostaglandin. For conveniencehereinafter, use of the terms PGE PGF and PGF will mean the opticallyactive form of that prostaglandin with the same absolute configurationas PGE obtained from mammalian tissues. When reference to the racemicform of one of those prostaglandins is intended, the word racemic willprecede the prostaglandin name, thus, racemic PGE or racemic PGF Each ofthe novel prostanoic acid derivatives of this invention is encompassedby the following formula or by the combination of that formula and itsmirror image:

I HO R; OH

In formula V, R, is hydrogen, alkyl of one to 8 carbon atoms, inclusive,or a pharmacologically acceptable cation, and R is methyl or ethyl.

In formula V, the configuration of the hydroxy at Cl5 is R as in theknown prostaglandins of formulas II to IV.

A significant characteristic of all of the known prostaglandins is thesecondary S hydroxy group at C-l5, i.e., the atom grouping f 11 \OHProstaglandins obtained from animal tissues always contain that atomgrouping. In striking contrast, each of the novel prostanoic acidderivatives of this invention has a tertiary R hydroxy group at C-15,i.e., the atom grouping acid derivatives of this invention also includethe corresponding racemic compounds. Formula V plus its mirror image arenecessary in combination to describe a racemic compound. For conveniencehereinafter, when the Word racemic precedes the name of one of the novelprostanoic acid derivatives of this invention, the intent is todesignate a racemic compound represented by the combination of theappropriate formula V and the mirror image of that formula. When theword racemic does not precede the compound name, the intent is todesignate an optically active compound represented only by theappropriate formula V and with the same absolute configuration as PGEobtained from animal tissues.

PGE, and its esters and pharmacologically acceptable salts are extremelypotent in causing various biological responses. For that reason, thesecompounds are useful for pharmacological purposes. See, for example,Bergstrom et al., Pharmacol. Rev. 20, 1 (1968), and references citedtherein. A few of those biological response are systemic arterial bloodpressure lowering as measured, for example, in anesthetized(pentobarbitol sodium) pentolinium-treated rats with indwelling aorticand right heart cannulas; stimulation of smooth muscle as shown, forexample, by tests on strips of guinea pig ileum, rabbit duodenum, orberbil colon; potentiation of other smooth muscle stimulants;antilipolytic activity as shown by antagonism of epinephrine-inducedmobilization of free fatty acids or inhibition of the spontaneousrelease of glycerol from isolated rat fat pads; inhibition of gastricsecretion as shown in dogs with secretion stimulated by food orhistamine infusion; activity on the central nervous system; decrease ofblood platelet adhesiveness as shown by platelet-to-glass adhesiveness,and inhibition of blood platelet aggregation and thrombus formationinduced by various physical stimuli, e.g., arterial injury, and variousbiochemical stimuli, e.g., ADP, ATP, serontonin, thrombin, and collagen;and stimulation of epidermal proliferation and keratinization as shownwhen applied in culture to embryonic chick and rat skin segments.

Because of these biological responses, these known prostaglandins areuseful to study, prevent, control, or alleviate a wide variety ofdiseases and undesirable physiological conditions in birds and mammals,including humans, useful domestic animals, pets, and zoologicalspecimens, and in laboratory animals, for example, mice, rats, rabbits,and monkeys.

For example, these compounds are useful in mammals, including man, asnasal decongestants. For this purpose, the compounds are used in a doserange of about g. to about 10 mg. per ml. of a pharmacologicallysuitable liquid vehicle or as an aerosol spray, both for topicalapplication.

PGE compounds are useful in mammals, including man and certain usefulanimals, e.g., dogs and pigs, to reduce and control excessive gastricsecretion, thereby reducing or avoiding gastrointestinal ulcerformation, and accelerating the healing of such ulcers already presentin the gastrointestinal tract. For this purpose, the compounds areinjected or infused intravenously, subcutaneously, or intramuscularly inan infusion dose range about 0.1 g. to about 500 g. per kg. of bodyweight per minute, or in a total daily dose by injection or infusion inthe range about 0.1 to about mg. per kg. of body weight per day, theexact dose depending on the age, weight, and condition of the patient oranimal, and on the frequency and route of administration.

PGE compounds are useful whenever it is desired to inhibit plateletaggregation, to reduce the adhesive character of platelets, and toremove or prevent the formation of thrombi in mammals, including man,rabbits, and rats. For example, these compounds are useful in thetreatment and prevention of myocardial infarcts, to treat and preventpost-operative thrombosis, to promote patency of vascular graftsfollowing surgery, and to treat conditions such as atherosclerosis,arteriosclerosis, blood clotting defects due to lipemia, and otherclinical conditions in which the underlying etiology is associated withlipid imbalance or hyperlipidemia. For these purposes, these compoundsare administered systemically, e.g., intravenously, subcutaneously,intramuscularly, and in the form of sterile implants for prolongedaction. For rapid response especially in emergency situations, theintravenous route of administration is preferred. Doses in the rangeabout 0.005 to about 20 mg. per kg. of body weight per day are used, theexact dose depending on the age, weight, and condition of the patient oranimal, and on the frequency and route of administration.

PGE compounds are especially useful as additives to blood, bloodproducts, blood substitutes, and other fluids which are used inartificial extracorporeal circulation and perfusion of isolated bodyportions, e.g., limbs and organs, whether attached to the original body,detached and being preserved or prepared for transplant, or attached toa new body. During these circulations and perfusions, aggregatedplatelets tend to block the blood vessels and portions of thecirculation apparatus. This blocking is avoided by the presence of thesecompounds. For this purpose, the compound is added gradually or insingle or multiple portions to the circulating blood, to the blood ofthe donor animal, to the perfused body portion, attached or detached, tothe recipient, or to two or all of those at a total steady state dose ofabout .001 to 10 mg. per liter of circulating fluid. It is especiallyuseful to use these compounds in laboratory animals, e.g., cats, dogs,rabbits, monkeys, and rats, for these purposes in order to develop newmethods and techniques for organ and limb transplants.

PGE compounds are extremely potent in causing stimulation of smoothmuscle, and are also highly active in potentiating other known smoothmuscle stimulators, for example, oxytocin agents, e.g., oxytocin, andthe various ergot alkaloids including derivatives and analogs thereof.Therefore PGE for example, is useful in place of or in combination withless than usual amounts of these known smooth muscle stimulators, forexample, to relieve the symptoms of paralytic ileus, or to control orprevent atonic uterine bleeding after abortion or delivery, to aid inexpulsion of the placenta, and during the puerperium. For the latterpurpose, the PGE compound is administered by intravenous infusionimmediately after abortion or delivery at a dose in the range about 0.01to about 50 g. per kg. of body weight per minute until the desiredeffect is obtained. Subsequent doses are given by intravenous,subcutaneous, or intramuscular injection or infusion during puerperiumin the range 0.01 to 2 mg. per kg. of body weight per day, the exactdose depending on the age, weight, and condition of the patient oranimal.

PGE compounds are useful as hypotensive agents to reduce blood pressurein mammals, including man. For this purpose, the compounds areadministered by intravenous infusion at the rate about 0.01 to about 50g. per kg. of body weight per minute, or in single or multiple doses ofabout 25 to 500 g. per kg. of body weight total per day.

PGE compounds are useful in place of oxytocin to induce labor inpregnant female animals, including man, cows, sheep, and pigs, at ornear term, or in pregnant animals with intrauterine death of the fetusfrom about 20 weeks to term. For this purpose, the compound is infusedintravenously at a dose 0.01 to 50 g. per kg. of body weight per minuteuntil or near the termination of the second stage of labor, i.e.,expulsion of the fetus. These compounds are especially useful when thefemal is one or more weeks post-mature and natural labor has notstarted, or 12 to 60 hours after the membranes have ruptured and naturallabor has not yet started.

PGE compounds are useful for controlling the repro ductive cycle inovulating female mammals, including humans and animals such as monkeys,rats, rabbits, dogs, cattle, and the like. For that purpose, PGE, forexample, is administered systemically, e.g., intravenously,subcutaneously, and intravaginally, at a dose level in the range 0.001mg. to about 200 mg. per kg. of body weight of the female mammal,advantageously during a span of time starting approximately at the timeof ovulation and ending approximately at the next expected time ofmenses or just prior to that time. Additionally, expulsion of an embryoor fetus is accomplished by similar administration of the compoundduring the first third of the normal mammalian gestation period.

PGE compounds are useful in female mammals, including humans and usefuldomestic animals, e.g., dogs and cattle, to produue cervical dilation.This has practical applications in labor induction and abortion wherethe cervix must be dilated. PGE compounds are also useful in dilationand curettage (D & C) to soften the cervix so that it need not bestreched entirely by mechanical means.

As mentioned above, PGE compounds are potent antagonists ofepinephrine-induced mobilization of free fatty acids. For this reason,these compounds are useful in experimental medicine for both in vitroand in vivo studies in mammals, including man, rabbits, and rats,intended to lead to the understanding, prevention, symptom alleviation,and cure of diseases involving abnormal lipid mobilization and high freefatty acid levels, e.g., diabetes mellitus, vascular diseases, andhyperthyroidism.

The novel IS-methyl and l5-ethyl prostaglandin analogs encompassed byformula V each cause the same biological responses described above forthe corresponding known prostaglandins. Each of these IS-methyl andIS-ethyl compound is accordingly useful for the abovedescribedpharmacological purposes, and is used for those purposes as describedabove. However, each of these methyl and IS-ethyl prostaglandin analogsis surprisingly and unexpectedly more useful than the correspondingknown prostaglandin for at least one of the pharmacological purposesdescribed above because for that purpose the analog is more potent andhas a substantially longer duration of activity. For that reason, fewerand smaller doses of these prostaglandin analogs are needed to attainthe desired pharmacological results.

The novel PGE-type analogs encompassed by formula V are used asdescribed above in the free acid form, in alkyl ester form, or inpharmacologically acceptable salt form. When the ester form is used, anyalkyl ester can be used wherein the alkyl moiety contains one to 8carbon atoms, inclusive, i.e., methyl, ethyl, propyl, butyl, pentyl,hexyl, heptyl, octyl, and isomeric forms thereof. However, it ispreferred that the ester be alkyl of one to four carbon atoms,inclusive. Of those alkyl, methyl and ethyl are especially preferred foroptimum absorption of the compound by the body or experimental animalsystem.

Pharmacologically acceptable salts of these prostaglandin analogs usefulfor the purposes described above are those with pharmacologicallyacceptable metal cations, ammonium, amine cations, or quaternaryammonium cations.

Especially preferred metal cations are those derived from the alkalimetals, e.g., lithium, sodium and potassium, and from the alkaline earthmetals, e.g., magnesium and calcium, although cationic forms of othermetals, e.g., aluminum, zinc, and iron, are within the scope of thisinvention.

Pharmacologically acceptable amine cations are those derived fromprimary, secondary, or tertiary amines. Examples of suitable amines aremethylamine, dimethylamine, trimethylamine, ethylamine, dibutylamine,triisopropylamine, N-methylhexylamine, decylamine, dodecylamine,allylamine, crotylamine, cyclopentylamine, dicyclohexylamine,benzylamine, dibenzylamine, a-phenylethylamine, ,B-phenylethylamine,ethylenediamine, diethylenetriamine, and like aliphatic, cycloaliphatic,and araliphatic amines containing up to and including about 18 carbonatoms, as well as heterocyclic amines, e.g., piperidine, morpholine,pyrrolidine, piperazine, and lower-alkyl derivatives thereof, e.g.,l-methylpiperidine, 4-ethylmorpholine, l-isopropylpyrrolidine,Z-methylpyrrolidine, 1,4- dimethylpiperazine, Z-methylpiperidine, andthe like, as Well as amines containing water-solubilizing or hydrophilic.groups, e.g., mono-, di-, and triethanolamine, ethyldiethanolamine,N-butylethanolamine, Z-amino-l-butanol, 2-amino-2-ethyl-1,3-propanediol,Z-amino-Z-methyl-l-propanol, tris(hydroxymethyl)aminomethane,N-phenylethanolamine, N-(p-tert-amylphenyl)diethanolamine, galactamine,N-methylglucamine, N-methylglucosamine, ephedrine, phenylephrine,epinephrine, procaine, and the like.

Examples of suitable pharmacologically acceptable quaternary ammoniumcations are tetramethylammonium, tetraethylammonium,benzyltrimethylammonium, phenyltriethylammonium, and the like.

As discussed above, the prostaglandin analogs are administered invarious Ways for various purposes; e.g., intravenously, intramuscularly,subcutaneously, orally, intravaginally, rectally, buccally,sublingually, topically, and in the form of sterile implants forprolonged action.

For intravenous injection or infusion, sterile aqueous isotonicsolutions are preferred. For that purpose, it is preferred because ofincreased water solubility to use the free acid form or thepharmacologically acceptable salt form. For subcutaneous orintramuscular injection, sterile solutions or suspensions of the acid,salt, or ester form in aqueous or non-aqueous media are used. Tablets,capsules, and liquid preparations such as syrups, elixirs, and simplesolutions, with the usual pharmaceutical carriers are used for oral orsublingual administration. For rectal or vaginal administration,suppositories, tampons, ring devices, and preparations adapted togenerate sprays or foams or to be used for lavage, all prepared as knownin the art, are used. For tissue implants, a sterile tablet or siliconerubber capsule or other object containing or or 2 fluoro, chloro, oralkyl of one to 4 carbon atoms, in-

CHART A l (oxidation) VII \ COOR l (sllylation) HO VIII (hydrolysis)COOR The PGF ,,-type and PGF ,-type acids and esters used as startingmaterials (Chart B) are prepared by the sequence of transformationsshown in Chart A, wherein formulas VII, VIII, IX, X, and XI includeoptically active compounds as shown and raeemic compounds of thoseformulas and the mirror image thereof. Also in Chart A, R is methyl orethyl, R is hydrogen or alkyl of one to 8 carbon atoms, inclusive, andindicates attachment of hydroxy to the ring in alpha or betaconfiguration. Also in Chart A, A is alkyl of one to 4 carbon atoms,inclusive, aralkyl of 7 to 12 carbon atoms, inclusive, phenyl, or phenylsubstituted with one or 2 fluoro, chloro, or alkyl of one to 4 carbonatoms, inclusive, and R is alkyl of one to 8 carbon atoms, inclusive, orSi(A) wherein A is as defined above. The various As of a -Si(A) moietyare alike or different. For example, an -Si(A) can be trimethylsilyl,dimethylphenylsilyl, or methylphenylbenzylsilyl. Examples of alkyl ofone to 4 carbon atoms, inclusive, are methyl, ethyl, propyl, isopropyl,butyl, isobutyl, sec-butyl, and tert-butyl. Examples of aralkyl of 7 to12 carbon atoms, inclusive, are benzyl, phenethyl, aphenylethyl,3-phenylpropyl, a-naphthylmethyl, and 2-( 8- naphthyl)ethyl. Examples ofphenyl substituted with one or 2 fluoro, chloro, or alkyl of one to 4carbon atoms, inclusive, are p-chlorophenyl, m-fiuorophenyl, o-tolyl,2,4- dichlorophenyl, p-tert-butylphenyl, 4-ehloro 2 methylphenyl, and2,4-dichloro-3-methylphenyl.

In Chart A, the final novel PGF and PGF acid and ester analogs useful asintermediates in this invention are encompassed by formula XI.

The initial optically active reactants of formula VII in Chart A, i.e.,PGF and P6P and their alkyl esters are known in the art or are preparedby methods known in the art. See, for example, Bergstrom et al., citedabove, and US. Pat. No. 3,069,322. The initial racemic reactants offormula VII in Chart A, i.e., racemic PGFh, racemie PGF and alkyl estersof those are also known in the art or are prepared by methods known inthe art. See, for example, Just et al., J. Am. Chem. Soc. 91, 5364(1969) and Corey et al., J. Am. Chem. Soc. 90, 3245 (1968).

The known acids and esters of formula VII are transformed to thecorresponding intermediate 15-oxo acids and esters of formula VIII byoxidation with reagents such as 2,3-dichloro 5,6dicyano-l,4-benzoquinone, activated manganese dioxide, or nickelperoxide (see Fieser ct al., Reagents for Organic Synthesis, John Wiley& Sons, Inc., New York, N.Y., pp. 215, 637 and 731). These reagents areused according to procedures known in the art.

Referring again to Chart A, the intermediate compounds of formula VIIIare transformed to silyl derivatives of formula IX, respectively, byprocedures known in the art. See, for example, Pierce, Silylation ofOrganic Compounds, Pierce Chemical Co., Rockford, Ill. (1968). Bothhydroxy groups of the formula VIII reactants are thereby transformed to--OSi--(A) moieties wherein A is as defined above, and sufficient of thesilylating agent is used for that purpose according to known procedures.When R in the formula VIII intermediate is hydrogen, the --COOH moietythereby defined is simultaneously transformed to COOSi(A) additionalsilylating agent being used for this purpose. This later transformationis aided by excess silylating agent and prolonged treatment. When R informula VIII is alkyl, then R in formula IX will also be alkyl. Thenecessary silylating agents for these transformations are known in theart or are prepared by methods known in the art. See, for example, Post;Silicones and Other Organic Silicon Com- 8 pounds, Reinhold PublishingCorp., New York, NY. (1949).

Referring again to Chart A, the intermediate silyl compounds of formulaIX are transformed to the final compounds of formulas X+XI by firstreacting the silyl compound with a Grignard reagent of the formula R MgXwherein R is methyl'or ethyl, and X is chloro, bromo, or iodo. For thispurpose, it is preferred that X be bromo. This reaction is carried outby the usual procedure for Grignard reactions, using diethyl ether as areaction solvent and saturated aqueous ammonium chloride solution tohydrolyze the Grignard complex. The resulting disilyl or trisilyltertiary alcohol is then hydrolyzed with water to remove the silylgroups. For this purpose, it is advantageous to use a mixture of waterand sufiicient of a water-miscible solvent, e.g., ethanol, to give ahomogenous reaction mixture. The hydrolysis is usually complete in 2 to6 hours at 25 C., and is preferably carried out in an atmosphere of aninert gas, e.g., nitrogen or argon.

The mixture of 15-S and 15-R isomers obtained by this Grignard reactionand hydrolysis is separated by procedures known in the art forseparating mixtures of prostanoic acid derivatives, for example, bychromatography on neutral silica gel. In some instances, the lower alkylesters, especially the methyl esters of a pair of 15-8 and 15-R isomersare more readily separated by silica gel chromatography than are thecorresponding acids. In those cases, it is advantageous to esterify themixture of acids as described below, separate the two esters, and then,if desired, saponify the esters by procedures known in the art forsaponifieation of prostaglandins F.

The novel optically active PGE -type acids and esters of formula V areprepared by oxidation of the corresponding R PGF -type or PGF -typeacids and alkyl esters of formula XI. For this purpose, an oxidizingagent is used which selectively oxidizes secondary hydroxy groups tocarbonyl groups in the presence of carbon-carbon double bonds. Thesetransformations are shown in Chart B wherein formulas XI and XII includeoptically active compounds as shown and racemic compounds of thoseformulas and the mirror images thereof. Also in Chart B, R is methyl orethyl, R is hydrogen or alkyl of one to 8 carbon atoms, inclusive, andindicates attachment of hydroxy to the ring in alpha or betaconfiguration. The reactants and products of formulas XI and XII eachhave the 15-hydroxy in R configuration.

CHART B For the transformation of Chart B, the beta isomers of reactantsXI are preferred starting materials, although the corresponding alphaisomers are also useful for this purpose.

Oxidation reagents useful for the transformations set forth in Chart Bare known to the art. An especially useful reagent for this purpose isthe Jones reagent, i.e., acidified chromic acid. See J. Chem. Soc. 39(1946). Acetone is a suitable diluent for this purpose, and a slightexcess beyond the amount necessary to oxidize one of the secondaryhydroxy groups of the formula XI reactant is used. Reaction temperaturesat least as low as about C. should be used. Preferred reactiontemperatures are in the range 10 to 50 C. The oxidation proceeds rapidlyand is usually complete in about to about 20* minutes. The excessoxidant is destroyed, for example, by addition of a lower alkanol,advantageously, isopropyl alcohol, and the formula XII PGE-type productis isolated by conventional methods.

Examples of other oxidation reagents useful for the Chart Btransformations are silver carbonate on Celite' (Chem. Commun. 1102(1969)), mixtures of chromium trioxide and pyridine (Tetrahedron Letters3363 (1968), I. Am. Chem. Soc. 75, 422 (1953), and Tetrahedron, 18, 13511962) mixtures of sulfur trioxides in pyridine and dimethyl sulfoxide(I. Am. Chem. Soc. 89, 5505 1967) and mixtures ofdicyclohexylcarbodiimide and dimethyl sulfoxide (J. Am. Chem. Soc. 87,5661 (1965)).

Still another process for transforming the PGF-type compounds XI toPGE-type compounds XII is shown in Chart C, wherein formulas XI, XII,XIII, and XIV include optically active compounds as shown and racemiccompounds of those formulas and the mirror image thereof. In Chart C, Ahas the same definition as in Chart A above. Also in Chart C, R ismethyl or ethyl, R is hydrogen or alkyl of one to 8 carbon atoms,inclusive, R is hydrogen, alkyl of one to 8 carbon atoms, inclusive, or--Si(A) wherein A is as defined above.

CHART C HO XI l (silylation) OH XIII 1 (oxidation) l (hydrolysis) XII 10are useful for the above purpose at temperatures below about 25 C. Apreferred temperature range is about -3S to '50. At higher temperaturessome silylation of C9 hydroxyl groups as well as the C-11 hydroxylgroups occurs, whereas at lower temperatures the rate of silylation isundesirably slow. Examples of the silylamine type silylating agentssuitable for forming the formula XIII intermediates includepentamethylsilylamine, pentaethylsilylamine,N-trimethylsilyldiethyla'mine, 1,1,1-triethyl-N,N-dimethylsilylamine,N,N-diisopropyl-1,l, ltrimethylsilylamine,1,1,1tributyl-N,N-dimethylsilylamine, N,N- dibutyl- 11,1-trimethy1silylamine, 1-is0butyl-N,N,1, l-tetramethylsilylamine, Nbenzyl-N-ethyl-1,1,l-trimethylsilylamine,N,N,1,1tetramethyl-l-phenylsilylamine, N,N-diethyl-1,1-dimethyl 1phenylsilylamine, N,N-diethyl-1- methyl-1,l-diphenylsilylamine,N,N-dibutyl-1,1,1-triphenylsilylamine, andl-methyl-N,N,1,l-tetraphenylsilylamine.

The reaction is carried out with exclusion of atmospheric moisture, forexample under a nitrogen atmosphere. It is conveniently done in asolvent such as acetone or dichloromethane, although the silylatingagent itself, when used in excess, may also serve as a liquid medium forthe reaction. The reaction ordinarily is completed in a few hours, andshould be terminated when the C-11 hydroxyl groups are silylated toavoid side reactions. The progress of the reaction is convenientlymonitored by thin-layer chromatography (TLC), utilizing methods known inthe art.

Trisubstituted mono-chlorosilanes such as chlorotriphenylsilane willalso yield formula XIII ll-substituted intermediates under suitableconditions of temperature and time of reaction. For the above purpose,these reagents are used in the presence of a tertiary base such aspyridine at temperatures of or below 25 0., preferably in the range ofabout 0 to +25 C. Examples of the trisubstituted' monochlorosilanessuitable for this purpose include chlorotriethylsilane,chlorotriisobutylsilanc, chlorotriphenylsilane,chlorotris(p-chlorophenyl)silane, chlorotri-m-tolylsilane, andtribenzylchlorosilane. As in using the silylamines above, the progressof the reaction is monitored by TLC and the conditions for optimizedll-silylation are determined by experimentation.

For either of the above types of silylating agents, an excess of thereagent over that stoichiometrically required is used, preferably atleast a four-fold excess. When R in the formula XI starting material ishydrogen the COOH moiety thereby defined may be partially or evencompletely transformed to CO0-Si(A) additional silylating agent beingused for this purpose. Whether or not this occurs is immaterial, sinceOOOH groups are not changed by the subsequent steps and groups areeasily hydrolyzed to COOH groups.

Consider, next, step 2 of Chart C, wherein the formula XIII ll-silylatedintermediate is oxidized to compound XIV. Oxidation reagents useful forthis transformation are known to the art. An especially useful reagentfor this purpose is the Collins reagent, i.e. chromium trioxide inpyridine. See J. C. Collins et al., Tetrahedron Lett., 3363 (1968).Dichloromethane is a suitable diluent for this purpose. A slight excessof the oxidant beyond the amount necessary to oxidize the C-9 secondaryhydroxy group of the formula XIII intermediate is used. Reactiontemperatures of below 20 C. should be used. Preferred reactiontemperatures are in the range --10 to l-lO C. The oxidation proceedsrapidly and is usually complete in about 5 to 20 minutes. The formulaXIV 15-alkyl PGE-type intermediate is isolated by conventional methods.

Examples of other oxidation reagents useful for this transformation arethose named above in connection with Chart B, including silver carbonateon Celite and also t-butylchromate in pyridine (Biochem. 1., 84, (1962)Finally in step 3 of Chart C, all silyl groups of the formula XIVintermediates are removed by hydrolysis,

thereby forming the formula XII PGE-type products. These hydrolyses arecarried out by prior art procedures known to be useful for transformingsilyl ethers and silyl esters to alcohols and carboxylic acids,respectively. See, for example, Pierce cited above, especially p. 447thereof. A mixture of water and sufiicient of a water-miscible organicdiluent to give a homogeneous hydrolysis reaction mixture represents asuitable reaction medium. Addition of a catalytic amount of an organicor inorganic acid hastens the hydrolysis. The length of time requiredfor the hydrolysis is determined in part by the hydrolysis temperature.With a mixture of water and methanol at 25 C., several hours is usuallysufficient for hydrolysis. At C., several days is usually necessary.

As discussed above, the processes of Charts A, B, and C lead either toacids (R is hydrogen) or to alkyl esters (R is alkyl of one to 8 carbonatoms, inclusive). When a formula XII PGE -type acid has been preparedand an alkyl ester is desired, esterification is advantageouslyaccomplished by interaction of the acid with the appropriatediazohydrocarbon. For example, when diazomethane is used, the methylesters are produced. Similar use of diazoethane, diazobutane, and1-diazo-2-ethylhexane, for example, gives the ethyl, butyl, and2-ethylhexyl esters, respectively.

Esterification with diazohydrocarbons is carried out by mixing asolution of the diazohydrocarbon in a suitable inert solvent, preferablydiethyl ether, with the acid reactant, advantageously in the same or adifferent inert diluent. After the esterification reaction is complete,the solvent is removed by evaporation, and the ester purified if desiredby conventional methods, preferably by chromatography. It is preferredthat contact of the acid reactants with the diazohydrocarbon be nolonger than necessary to effect the desired esterification, preferablyabout one to about ten minutes, to avoid undesired molecular changes.Diazohydrocarbons are known in the art or can be prepared by methodsknown in the art. See, for example, Organic Reactions, John Wiley &Sons, Inc., New York, N.Y., Vol. 8, pp. 389-394 (1954).

An alternative method for esterification of the carboxyl moiety of thePGE-type compounds comprises transformation of the free acid to thecorresponding silver salts, followed by interaction of that salt with analkyl iodide. Examples of suitable iodides are methyl iodide, ethyliodide, butyl iodide, isobutyl iodide, tert-butyl iodide, and the like.The silver salts are prepared by conventional methods for example, bydissolving the acid in cold dilute aqueous ammonia, evaporating theexcess ammonia at reduced pressure, and then 'adding the stoichiometricamount of silver nitrate.

The novel formula XII acids (R is hydrogen) are transformed topharmacologically acceptable salts by neutralization with appropriateamounts of the corresponding inorganic or organic base, examples ofwhich correspond to the cations and amines listed above. Thesetransformations are carried out by a variety of procedures known in theart to be generally useful for the preparation of inorganic, i.e., metalor ammonium, salts, amine acid addition salts, and quaternary ammoniumsalts. The choice of procedure depends in part upon the solubilitycharacteristics of the particular salt to be prepared. In the case ofthe inorganic salts, it is usually suitable to dissolve the acid inwater containing the stoichiometric amount of a hydroxide, carbonate, orbicarbonate corresponding to the inorganic salt desired. For example,such use of sodium hydroxide, sodium carbonate, or sodium bicarbonategives a solution of the sodium salt of the prostanoic acid derivative.Evaporation of the water or addition of a watermiscible solvent ofmoderate polarity, for example, a lower alkanol or a lower alkanone,gives the solid inorganic salt if that form is desired.

To produce an amine salt, the acid is dissolved in a suitable solvent ofeither moderate or low polarity. Examples of the former are ethanol,acetone, and ethyl acetate. Examples of the latter are diethyl ether andbenzene. At least a stoichiometric amount of the amine corresponding tothe desired cation is then added to that solution. If the resulting saltdoes not precipitate, it is usually obtained in solid form by additionof a miscible diluent of low polarity or by evaporation. If the amine isrelatively volatile, any excess can easily be removed by evaporation. Itis preferred to use stoichiometric amounts of the less volatile amines.

Salts wherein the cation is quaternary ammonium are produced by mixingthe acid with the stoichiometric amount of the corresponding quaternaryammonium hydroxide in water solution, followed by evaporation of thewater.

The invention can be more fully understood by the following examples.

Infrared adsorption spectra are recorded on a Perkin- Elmer model 421infrared spectrophotometer. Undiluted (neat) samples of the liquids andoils are used. Mineral oil (Nujol) mulls of the solids are used.

NMR spectra are recorded on a Varian A-60 spectrophotometer withtetramethylsilane as an internal standard (downfield) and using solventsas indicated below.

Mass spectra are recorded on an Atlas CH-4 mass spectrometer with a TO-4source (ionization voltage ev.).

The term 15-oxoin front of a compound name, e.g., 15-oxo-PGF refers to aprostaglandin analog wherein the moiety at the 15position has beentransformed to Example 1.-15-Oxo-PGF 2,3 Dichloro 5,6dicyano-1,4-benzoquinone (463 mg.) is added to a soltuion of PGF (600mg.) in 30 ml. of dioxane. The mixture is stirred 24 hours at 50 C.under nitrogen, and then is cooled to 20 C. and filtered. The filteredsolids are washed with dichloromethane. Evaporation of the combinedfiltrate and washings at reduced pressure gives 650 mg. of a residuewhich is chromatographed on 150 g. of silica gel (Silicar CC-4;Mallinckrodt), eluting with 50% ethyl acetate in Skellysolve B (amixture of isomeric hexanes). Evaporation of the eluates gives 545 mg.of 15-oxo-PGF infrared absorption at 3400, 2660, 1700, 1660, 1620, 1460,1410, 1375, 1285, 1250, 1185, 1120, 1070, and 980 CHIS-1.

Example 2.15-Oxo-PGF 2,3-Dichloro-5,6-dicyano-1,4 benzoquinone (1.0 g.)is added to a solution of PGF (1.3 g.) in 80 ml. of dioxane. The mixtureis stirred 24 hours at 50 C. under nitrogen, and is then cooled to 20 C.and filtered. The filtered solids are washed with dichloromethane.Evaporation of the combined filtrate and washings at reduced pressuregives 1.6 g. of a residue which is chromatographed on 400 g. of silicagel (Silicar CC-4; Mallinckrodt) eluting with ethyl acetate inSkellysolve B. Evaporation of the eluates gives 1.15 g. of 15-0xo-PGFinfrared absorption at 3380, 2660, 1720, 1705, 1665, 1620, 1460, 1405,1370, 1325, 1285, 1235, 1190, 1080, 1040, and 980 omr Following theprocedure of Example 1, the methyl, ethyl, tert-butyl, and 2-ethylhexylesters of PGF and PGF are each oxidized to the corresponding15-oxocompounds.

Also following the procedure of Example 1, the racemic forms of PGF andPGF and the methyl, ethyl, tertbutyl, and 2-ethylhexy1 esters of each ofthose are each oxidized to the corresponding racemic 15-oxo compound.

mma. 3.Tris-(trimethylsilyl) Derivatives of 15-Oxo- Example4.-Tris-(trimethylsilyl) Derivatives of 15-Oxo- Following the procedureof Example 3, l5-oxo-PGF is transformed to the tris-(trimethylsilyl)derivative; infrared absorpton at 1725, 1680, 1635, 1365, 1250, 1180,

1065, 980, 840, and 750 cm Following the procedure of Example 3, themethyl, ethyl, tert-butyl, and 2-ethylhexyl esters of 15-oxo-PGF and15-oxo-PGF are each transformed to the corresponding bis-(trimethylsilyl) derivative.

Also following the procedure of Example 3, the racemic forms of15-oxo-PGF and l5-oxo-PGF and the methyl, ethyl, tert-butyl, and2-ethylhexyl esters of each of those are each transformed totrimethylsilyl derivatives, the acids to tris derivatives and the estersto his derivatives.

Example 5.15-Methyl-15(R)-PGF A 3 molar diethyl ether solution ofmethylmagnesium bromide (0.55 ml.) is added dropwise to a stirred solu-'tion of the tris-(trimethylsilyl) derivative of 15-oxo-PGF h (850 mg.)in 25 ml. of diethyl ether at 25 C. The mixture is stirred 30 minutes at25 C., after which an additional 0.2 ml. of the methylmagnesium bromidesolution is added and stirring is continued an additional 30 minutes.The resulting reaction mixture is poured into 75 ml. of saturatedaqueous ammonium chloride solution at C. After stirring several minutes,the mixture is extracted repeatedly with diethyl ether. The combineddiethyl ether extracts are washed with saturated aqueous sodium chloridesolution and then dried with anhydrous sodium sulfate. Evaporation ofthe diethyl ether gives a yellow oil (910 mg.) which is dissolved in 45ml. of ethanol. That solution is diluted with 30 ml. of water, and themixture is stired 4 hours at 25 C. The ethanol in the resulting solutionis evaporated at reduced pressure, and the aqueous residue is saturatedwith sodium chloride and then extracted with ethyl acetate. The extractis washed with saturated aqueous sodium chloride solution, dried withanhydrous sodium sulfate, and evaporated under reduced pressure to give640 mg. of a mixture of 15-methyl-PGF and 15-methyl-15(R)-PGF infraredabsorption at 3280, 2600, and 1710 cm.-

The mixture of 15-methyl-PGF and 15-rnethyl-l5 (R)- PGF is dissolved in50 ml. of diethyl ether and cooled to 0 C. Excess diazomethane dissolvedin diethyl ether is then added, and the mixture is maintained 5 minutesat 0 C. and then 5 minutes at 25 C. The solution is evaporated in astream of nitrogen, and the residue is chromatographed on 550 g. ofneutral silica, eluting with 75% ethyl acetate in Skellysolve B.Evaporation of eluate fractions gives, successively, 127 mg. of-methyl-15(R)-PGF methyl ester, 150 mg. of a mixture of 15-methyl-15(R)-PGF methyl ester and IS-methyl-PGF methyl ester, and 228 mg. of15-methyl-PGF methyl ester.

Aqueous potassium hydroxide solution (45%; 0.7 ml.) is added to asolution of 15-methyl-15(R)-PGF methyl ester (151 mg.) in a mixture of4.4 ml. of methanol and 1.5 ml. of water under nitrogen. The resultingsolution is stirred 2 hours at C., and is then poured into severalvolumes of water. The aqueous mixture is extracted with ethyl acetate,acidified with 3 N hydrochloric acid, saturated with sodium chloride,and then extracted repeatedly with ethyl acetate. The latter ethylacetate extracts are combined, washed successively with water andsaturated aqueous sodium chloride solution, dried with anhydrous sodiumsulfate, and evaporated under reduced pressure to give15-methyl-15(R)-PGF in the form of an oil; infrared absorption at 3380,2650, 1710, 1460, 1410, 1375, 1275-1200, 1125, 1075, 1040 and 975 cmrNMR peaks (dimethylformamide) at 5.5 and 4.4-3.6 (multiplet) 6; massspectral molecular ion peaks at 352, 334, 316, and 263.

Following the procedure of Example 5, 15-oxo-PGF is transformed to15-methyl-15 (R)-PGF Also following the procedure of Example 5, themethyl, ethyl, tert-butyl, and 2-ethylhexyl esters of thebis-(trimethylsilyl derivatives) of 15-oxo-PGF and 15-oxo- PGF are eachtransformed to the corresponding 15- methyl-15(R) esters.

Also following the procedure of Example 5, the racemic forms of thetrimethylsilyl derivatives of 15-oxo-PGF and 15-oxo-PGF and the methyl,ethyl, tert-butyl, and 2-ethylhexyl esters of each of those, trisderivatives of the acids and bis derivatives of the esters, are eachtransformed to the corresponding l5-methy1-15(R) acid or esters.

Also following the procedure of Example 5 but using 2 ethylmagnesiumbromide in place of methylmagnesium bromide, the tris-(trimethylsilyl)derivatives of 15-oxo- PGF and IS-OXO-PGFM, and the racemic form of eachof those optically active acids, and also the bis(trimethylsilyl)derivative of the methyl, ethyl, tert-butyl, and 2- ethyl-hexyl ester ofeach of those optically active and racemic acids are each transformed tothe corresponding 15-ethyl-15(R) acid or ester.

Example 6.15-Methyl-15 (R) -PGE A solution of 15methyl-15(R)-PGF mg.) in40 ml. of acetone is cooled to 10 C. Jones reagent (0.1 ml. of asolution of 21 g. of chromic anhydride, 60 ml. of water, and 17 ml. ofconcentrated sulfuric acid), precooled to 0 C., is added with vigorousstirring. After 5 minutes at -10 C., thin layer chromatography on silicagel (acetic acidzmethanol:chloroform; 5:5:90) of a small portion of thereaction mixture indicates about 50% reaction completion. An additional0.06 ml. of Jones reagent is added to the still cold reaction mixturewith stirring, and the mixture is stirred an additional 5 minutes at 10C. Isopropyl alcohol (1 ml.) is added to the cold reaction mixture.After 5 minutes, the mixture is filtered through a layer of diatomaceousearth (Celite). The filtrate is evaporated at reduced pressure, and theresidue is mixed with 5 ml. of saturated aqueous sodium chloridesolution. The mixture is extracted repeatedly with ethyl acetate, andthe combined extracts are washed with saturated aqueous sodium chloridesolution, dried with anhydrous sodium sulfate, and evaporated at reducedpressure. The residue is chromatographed on 20 g. of neutral silica gel,eluting with 50% ethyl acetate in Skellysolve B. Evaporation of theeluates gives 15-methyl- 15 (R)-PGE Following the procedure of Example6, 15 methyl- 15 (R)-PGF is oxidized to 15-methyl-15(R)-PGE Alsofollowing the procedure of Example 6, the methyl, ethyl, tert-butyl, and2-ethylhexy1 esters of IS-methyl- 15(R)-PGF and IS-methyl 15(R) PGF areeach oxidized to the corresponding IS-methyl 15 (R) PGE; ester.

Also following the procedure of Example 6, the racemic forms of 15methyl 15(R) l PGF and 15 methyl- 15 (R)-PGF and the methyl, ethyl,tert-butyl, and 2- ethylhexyl esters of each of those racemic acids areeach oxidized to the corresponding 15-methyl-15 (R)-PGE acid or ester.

Also following the procedure of Example 6, 15-ethyl- 15(R)-PGF and 15ethyl 15(R) PGF and the racemic forms of each of those optically activeacids, and the methyl, ethyl, tert-butyl, and 2-ethylhexyl ester of eachof those optically active and racemic acids are each oxidized to thecorresponding 15-ethyl-l5(R)-PGE acid or ester.

Example 7.--15-Methyl-15 (R) -PGE,

A. Refer to Chart C. There is first prepared 15-methy1- 15(R)-PGFll-trimethylsilyl ether. N-Trimethylsilyldiethylamine (2 ml.) is addedslowly to a mixture of 15- methyl 15 (R) PGF (Example 5, 0.5 g.) and ml.of acetone previously cooled to --45 C., and kept under nitrogen.Progress of the reaction is monitored by thinlayer chromatography (TLC).The reaction temperature is maintained at --40 to -45" C. for one hourwhereupon the mixture is diluted with 80 ml. of diethyl ether(previously cooled to 78 C.). The solution is washed with 200 ml. ofcold saturated sodium bicarbonate solution. The organic phase is washedwith brine, dried over sodium sulfate, and concentrated to yield 15methyl- 15 (R) -PGF ll-trimethylsilyl ether.

B. A solution of the product of step A (0.6 g.) in 15 ml. ofdichloromethane is added to Collins reagent, prepared from chromiumtrioxide (1.0 g.) and pyridine (1.6 g.) in 50 ml. of dichloromethane andcooled to 0 C. The mixture is stirred for 30 min. at about C., thenfiltered. The filtrate is concentrated to yield 15-methyl 15(R)- PGEll-trimethylsilyl ether.

C. A solution of the product of step B (0.5 g.) in ml. of methanol ismixed with 15 ml. of water at about 25 C. and stirred for about 15 min.The mixture is partitioned between diethyl ether and 2 M. sodiumhydrogen sulfate. The ether extract is washed with saturated aqueoussodium bicarbonate and brine, dried over sodium sulfate, andconcentrated. The residue is chromatographed on silica gel, combiningthose fractions shown by TLC to contain the product free of startingmaterial and impurities, and concentrating to yield the title compound.

1 6 Example 8.-Racemic 15-Methyl-15(R)-PGE Following the procedures ofExample 7, the racemic form of 15-methyl-15(R)-PGF (Example 5) istransformed to the title compound.

I claim:

1. An optically active compound of the formula:

References Cited UNITED STATES PATENTS 3,514,383 5/1970 Beal III et al.209158 OTHER REFERENCES Ramwell et al.: Nature 221, 1251 (1969). Pike etal.: J. O. C. 34, 3552 (1969). Corey et al.: JACS 90, 3245 (1968).

ROBERT GERSTL, Primary Examiner US. Cl. X.R.

260211 R, 247.2 R, 268 R, 293.65, 326.3, 429.9, 430, 459 R, 448 R, 448.8R, 468 D, 501.1, 501.15, 501.17, 501.2; 424305, 317

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3, 9, 7Dated November 19, 197

fl wfl Gordon L. Buncl It in certified that error appears theabove-identified patentand that said Letters Patent are hereby correctedas shown below:

Column 3, line 25, "berbil" should read gerbil line 36,

'serontoni n" should read -serotoni n Column l, l ine 36,

- "oxytocin" shouldread oxytocic line 67 "femal" should read femaleColumn 6, l i ne 35, or 2 -Fluoro, chloro, or

al kyl of one to l carbon atoms, i n-" should read impregnated with thesubstance is used Column 12, line 17 "adsorption" should' readabsorption line 55 '15position" should read 15-position Column 13, linel8 "stired" should read stirred Column 14, line 69 15(R) 1 -PGF shouldread Signed and sealed this lst day of April 1975.

(SEAL) Attest:

- C. P'ZARSE; LL DAMN RUTH C. IZASOf-T Commissioner of Patents AttestingOfficer and Trademarks roan no-aoso uo-m

1. AN OPTICALLY ACTIVE COMPOUND OF THE FORMULA: